protocol and abc

tests/test_protocol.py

@@ -1,12 +1,13 @@
 import io
 
+from rich.abc import RichRenderable
 from rich.console import Console
 from rich.panel import Panel
 from rich.text import Text
 
 
 class Foo:
-    def __rich__(self):
+    def __rich__(self) -> Text:
         return Text("Foo")
 
 
@@ -22,3 +23,13 @@ def test_rich_cast_container():
     console = Console(file=io.StringIO(), legacy_windows=False)
     console.print(Panel.fit(foo, padding=0))
     assert console.file.getvalue() == "╭───╮\n│Foo│\n╰───╯\n"
+
+
+def test_abc():
+    foo = Foo()
+    assert isinstance(foo, RichRenderable)
+    assert isinstance(Text("hello"), RichRenderable)
+    assert isinstance(Panel("hello"), RichRenderable)
+    assert not isinstance(foo, str)
+    assert not isinstance("foo", RichRenderable)
+    assert not isinstance([], RichRenderable)